Solve for $x$ and $y$ using substitution. ${-x-y = 5}$ ${x = 4y-10}$
Answer: Since $x$ has already been solved for, substitute $4y-10$ for $x$ in the first equation. ${-}{(4y-10)}{- y = 5}$ Simplify and solve for $y$ $-4y+10 - y = 5$ $-5y+10 = 5$ $-5y+10{-10} = 5{-10}$ $-5y = -5$ $\dfrac{-5y}{{-5}} = \dfrac{-5}{{-5}}$ ${y = 1}$ Now that you know ${y = 1}$ , plug it back into $\thinspace {x = 4y-10}\thinspace$ to find $x$ ${x = 4}{(1)}{ - 10}$ $x = 4 - 10$ ${x = -6}$ You can also plug ${y = 1}$ into $\thinspace {-x-y = 5}\thinspace$ and get the same answer for $x$ : ${-x - }{(1)}{= 5}$ ${x = -6}$